Neutrophil response to Neisseria meningitidis: inhibition of adhesion molecule expression and phagocytosis by recombinant bactericidal/permeability-increasing protein (rBPI21)

Polymorphonuclear neutrophil (PMNL) activation enhances microbial clearance but also contributes to the vascular damage and multiorgan failure associated with severe meningococcal sepsis. By use of a whole blood model of meningococcal bacteremia, loss of PMNL L-selectin and up-regulation of CD11b was observed in response to Neisseria meningitidis serogroups B and C, which is followed by opsonophagocytosis. PMNL priming with either Escherichia coli lipopolysaccharide (LPS) or FMLP prior to meningococcal challenge resulted in enhancement of both PMNL L-selectin shedding (1.5- to 4-fold) and phagocytosis (2- to 3-fold). Blockade of meningococcal LPS lipid A with recombinant bactericidal/permeability-increasing protein (rBPI21) resulted in partial inhibition of the PMNL activation and phagocytosis response to N. meningitidis. The effect of rBPI21 was reversed by excess E. coli LPS or FMLP. It is proposed that PMNL priming by N. meningitidis results in an exaggerated activation and phagocytosis response to the organism.

Humoral immune responses to Neisseria meningitidis in children

An understanding of the nature of immunity to serogroup B meningococci in childhood is necessary in order to establish the reasons for poor responses to candidate vaccines in infancy. We sought to examine the nature of humoral immune responses following infection in relation to age. Serum bactericidal activity was poor in children under 12 months of age despite recent infection with Neisseria meningitidis. The highest levels of bactericidal activity were seen in children over 10 years of age. However, infants produced levels of total immunoglobulin G (IgG) and IgG subclass antibodies similar to those in older children in a meningococcal enzyme-linked immunosorbent assay. Most antibody was of the IgG1 and IgG3 subclasses. This striking age dependency of bactericidal antibody response following infection is not apparently due to failure of class switching in infants but might be due to qualitative differences in antibody specificity or affinity.

Cellular immune responses to Neisseria meningitidis in children

There is an urgent need for effective vaccines against serogroup B Neisseria meningitidis. Current experimental vaccines based on the outer membrane proteins (OMPs) of this organism provide a measure of protection in older children but have been ineffective in infants. We postulated that the inability of OMP vaccines to protect infants might be due to age-dependent defects in cellular immunity. We measured proliferation and in vitro production of gamma interferon (IFN-gamma), tumor necrosis factor alpha, and interleukin-10 (IL-10) in response to meningococcal antigens by peripheral blood mononuclear cells (PBMCs) from children convalescing from meningococcal disease and from controls. After meningococcal infection, the balance of cytokine production by PBMCs from the youngest children was skewed towards a TH1 response (low IL-10/IFN-gamma ratio), while older children produced more TH2 cytokine (higher IL-10/IFN-gamma ratio). There was a trend to higher proliferative responses by PBMCs from older children. These responses were not influenced by the presence or subtype of class 1 (PorA) OMP or by the presence of class 2/3 (PorB) or class 4 OMP. Even young infants might be expected to develop adequate cellular immune responses to serogroup B N. meningitidis vaccines if a vaccine preparation can be formulated to mimic the immune stimulus of invasive disease, which may include stimulation of TH2 cytokine production.

A bioluminescence method for the mapping of local ATP concentrations within the arterial wall, with potential to assess the in vivo situation

According to the anoxemia theory of atherosclerosis, an imbalance between the demand for and supply of oxygen and nutrients in the arterial wall is a key factor in atherogenesis. However, the energy metabolic state of the arterial tissue in vivo is largely unknown. We applied a bioluminescence method, metabolic imaging, to study local ATP concentrations in cryosections of normal pig and atherosclerotic and normal rabbit aorta. Some vessels were subjected to energy metabolic restrictions by incubation at different oxygen and glucose concentrations and others were rapidly frozen in liquid nitrogen to reflect the in vivo situation. Local ATP concentrations and the ATP distribution at a microscale was dependent on oxygen as well as glucose concentrations during incubation. ATP depletion was seen in the mid media of pig aorta in all incubations, but only at low oxygen concentration without glucose in the media of the thinner rabbit aorta. ATP-depleted zones were seen deep in pig media (>750 microm from the lumen) and in rabbit plaques (>300 micrometer+ from the lumen) even at high oxygen (pig 75% O2 and rabbit 21% O2) and glucose concentrations (5.6 mmol/L glucose). This observation probably illustrates an insufficient diffusion of glucose, which highlights the importance of studying the conditions for diffusion not only of oxygen but also of other metabolites in the arterial wall. In rapidly frozen vessels the medial ATP concentration was shown to be 0.6 to 0.8 micromol/g wet weight (both pig and rabbit aorta) and in pig aorta a gradient could be seen indicating higher ATP concentrations at the lumenal side. We propose that metabolic imaging, as applied to snap-frozen tissue, may be used to assess the energy metabolic situation in the arterial wall in vivo. The spatial resolution allows the detection of local variations within the arterial tree. However, steep concentration gradients (eg, near the border of the tissue) will be underestimated. The method may be extended to include determinations of glucose and lactate concentrations and will be used in parallel with an established method to assess hypoxia in the arterial wall in vivo.

Evidence of hypoxic areas within the arterial wall in vivo

The anoxemia theory of atherosclerosis states that an imbalance between the demand and supply of oxygen in the arterial wall is a key factor for the development of atherosclerotic lesions. Direct in vitro and in situ measurements have shown that PO2 is decreased in the more deeply situated parts of the media, but the degree of hypoxia in vivo or the distribution of hypoxia along the arterial tree is not known. For this reason, we have developed a method for the detection of hypoxia in the arterial wall in vivo by using a hypoxia marker, 7-(4'-(2-nitroimidazol-1-yl)-butyl)-theophylline, that may be visualized by immunofluorescence. In the present study, we have used this method in rabbits with experimentally induced atherosclerosis. Our results indicate that zones of hypoxia occur at depth in the atherosclerotic plaque. The mechanism was probably an impaired oxygen diffusion capacity due to the thickness of the lesion, together with high oxygen consumption by the foam cells. Thus, we have for the first time demonstrated that hypoxia actually does exist in the arterial wall in vivo, lending support to the anoxemia theory of atherosclerosis.

Association of variants of the gene for mannose-binding lectin with susceptibility to meningococcal disease. Meningococcal Research Group

BACKGROUND

The reasons why meningococcal disease develops in only a small proportion of individuals carrying the causative bacteria are unknown. Differences in host responses to bacterial colonisation are thought to be involved, since people with deficiencies in the terminal components of the complement pathway, or of properdin, are susceptible to meningococcal disease. We postulate that genetic variants of mannose-binding lectin (MBL), a plasma opsonin that initiates another pathway of complement activation, might similarly cause susceptibility to meningococcal disease.

METHODS

The frequency of variants of the MBL gene was ascertained in children with meningococcal disease and controls from two independent studies; one hospital-based (194 patients and 272 controls [patients with non-infectious disorders]), and one community-based (72 patients and 110 controls [healthy individuals]), by means of PCR and restriction-enzyme digestion, with confirmation by DNA sequencing.

FINDINGS

The proportion of people homozygous for MBL-variant alleles was higher in patients with meningococcal disease than in controls in the hospital study (15 [7.7%] vs four [1.5%]; odds ratio 6.5 [95% CI 2.0-27.2]) and in the community study (six [8.3%] vs three [2.7%]; 4.5 [0.9-29.1]). The population attributable fraction of cases attributable to MBL variants (homozygous and heterozygous) was 32%.

INTERPRETATION

The MBL pathway is a critical determinant of meningococcal-disease susceptibility, and genetic variants of MBL might account for a third of all disease cases.

Emergency management of meningococcal disease

Meningococcal disease remains a major cause of mortality in children in the UK. Aggressive early volume resuscitation, meticulous attention to the normalisation of all physiological and laboratory parameters, and prompt referral to specialist paediatric intensive care may lead to a sharp reduction in mortality. Application of the management algorithm described in this article may be helpful to those involved in the early part of management of critically ill patients with meningococcal disease.

Safety and immunogenicity of HIV recombinant envelope vaccines in HIV-infected infants and children. National Institutes of Health-sponsored Pediatric AIDS Clinical Trials Group (ACTG-218)

Study objectives were to evaluate the safety and immunogenicity of three HIV recombinant glycoproteins in HIV-infected infants and children between 1 month and 18 years of age with asymptomatic (P-1) infection. Using Chiron rgp 120 (SF-2) 15 or 50 microg; MicroGeneSys rgp 160 (IIIB) 40 or 320 microg; Genentech rgp120 (MN) 75 or 300 microg; or adjuvant control (Alum or MF-59), children were randomized to a double-blind, placebo-controlled, dose-escalating study of vaccine administered intramuscularly at entry and 1, 2, 3, 4, and 6 months later. No adverse events were attributed to study vaccines. Between 30% and 56% of volunteers exhibited a lymphoproliferative response as defined in terms of stimulation index (SI) to vaccine antigens; 65% of vaccinees but none of placebo recipients exhibited moderate or strong responses after enzyme immunoassay to HIV specific antigens. CD4 cell counts and quantitative HIV culture did not differ significantly among vaccine and control groups, nor were differences found among groups in HIV disease progression. The rgp160 and gp120 subunit vaccines were safe and immunogenic in this population.

CSF and MRI findings in patients with acute herpes zoster

OBJECTIVE

To explore MRI and CSF findings in patients with herpes zoster (HZ) and to correlate the findings with clinical manifestations of the disease.

METHODS

Fifty immunocompetent patients (mean age, 59 years; range, 17 to 84 years) with HZ of fewer than 18 days duration participated. None had clinical signs of meningeal irritation, encephalitis, or myelitis. In 42 patients (84%), the symptoms constituted pain and rash only. Six patients (12%) had motor paresis, and three patients (6%) had ocular complications. One to three CSF samples were obtained from 46 patients (the first sampling taken 1 to 18 days from onset of rash), and 16 patients (all with either trigeminal or cervical HZ) underwent MRI of the brain. The clinical follow-up continued at least 3 months.

RESULTS

CSF was abnormal in 28/46 patients (61%): pleocytosis (range, 5 to 1,440 microL) was detected in 21, elevated protein concentration in 12, varicella zoster virus (VZV) DNA in 10, and immunoglobulin G antibody to VZV in 10. These changes were more common in patients with acute complications, although they did not predict development of postherpetic neuralgia (PHN). In 9/16 patients (56%), MRI lesions attributable to HZ were seen in the brainstem and cervical cord. At 3 months, 5/9 patients (56%) with abnormal MRI had PHN, whereas none of the 7 patients with no HZ-related lesions on MRI had any remaining pain.

CONCLUSIONS

Subclinical extension of viral inflammation into the CNS occurs commonly in HZ. This finding may have implications for treatment of HZ and prevention of various associated complications.

Gap junctions are involved in the early generation of left-right asymmetry

Invariant left-right asymmetry of the visceral organs is a fundamental feature of vertebrate embryogenesis. While a cascade of asymmetrically expressed genes has been described, the embryonic mechanism that orients the left-right axis relative to the dorsoventral and anteroposterior axes (a prerequisite for asymmetric gene expression) is unknown. We propose that this process involves dorsoventral differences in cell-cell communication through gap junctions composed of connexin proteins. Global modulation of gap junctional states in Xenopus embryos by pharmacological agents specifically induced heterotaxia involving mirror-image reversals of heart, gut, and gall bladder. Greatest sensitivity was observed between st. 5 and st. 12, well before the onset of organogenesis. Moreover, heterotaxia was also induced following microinjection of dominant negative and wild-type connexin mRNAs to modify the endogenous dorsoventral difference in junctional communication. Heterotaxia was induced by either blocking gap junction communication (GJC) dorsally or by introducing communication ventrally (but not the reverse). Both connexin misexpression and exposure to GJC-modifying drugs altered expression of the normally left-sided gene XNR-1, demonstrating that GJC functions upstream of XNR-1 in the pathway that patterns left-right asymmetry. Finally, lineage analysis to follow the progeny of microinjected cells indicated that they generally do not contribute the asymmetric organs. Together with the early sensitivity window, this suggests that GJC functions as part of a fundamental, early aspect of left-right patterning. In addition, we show that a potential regulatory mutation in Connexin43 is sufficient to cause heterotaxia. Despite uncertainty about the prevalence of the serine364 to proline substitution reported in human patients with laterality defects, the mutant protein is both a mild hypomorph and a potent antimorph as determined by the effect of its expression on left-right patterning. Taken together, our data suggest that endogenous dorsoventral differences in GJC within the early embryo are needed to consistently orient left-right asymmetry.

Functionally active cardiac antibodies in chronic Chagas' disease are specifically blocked by Trypanosoma cruzi antigens

Antibodies of chronic chagasic patients have been shown to interfere with electric and mechanical activities of cardiac embryonic myocytes in culture and with whole mammalian hearts. A mechanism proposed for this effect involves interaction of the antibodies with G-protein-linked membrane receptors, thus leading to activation of beta adrenergic and muscarinic receptors; more specifically, IgG of chagasic patients would interact with the negatively charged regions of the second extracellular loop of these receptors. We performed competition experiments to test this hypothesis. We evaluated the effect of sera/IgG from patients previously known to depress electrogenesis and/or atrioventricular conduction in isolated rabbit hearts after incubation with live and lysed parasites, the peptide corresponding to the second extracellular loop (O2) of the M2 receptor, and different peptides derived from two ribosomal proteins of T. cruzi: P0 and P2beta. Our results indicate that 1) the antigenic factor inducing the functionally active IgGs in the chagasic patients is probably an intracellular T. cruzi antigen; 2) IgG/serum is interacting with the O2 region of the M2 receptor in the rabbit heart; and 3) the negative charges present in the ribosomal proteins of T. cruzi are important in mediating the interaction between the patients' serum/IgG and the receptor.

Avoidable deficiencies in the delivery of health care to children with meningococcal disease

OBJECTIVES

It is apparent that delays and inadequate or inappropriate management occur frequently and may contribute to the continued high mortality seen in meningococcal disease. An attempt has been made to define the major sources of delay or inappropriate treatment.

METHODS

A prospective, descriptive study of children with meningococcal disease referred to a tertiary centre paediatric intensive care and infectious disease unit. Definitions of optimal care were established at three stages: parental; general practitioner (GP)/accident and emergency (A&E) department; and hospital. Duration of symptoms and management were recorded from direct questioning of parents and carers, and from hospital records.

RESULTS

54 consecutive children with meningococcal disease were recruited to the study. Delayed parental recognition occurred in 16 children. GPs correctly diagnosed 19 of 35 children. Delay of 2.5-21 hours occurred in those who were incorrectly diagnosed. Two of 15 children who presented to the A&E department with specific features were incorrectly diagnosed. Hospital treatment was suboptimal in 71%. Shock was not recognised or treated in 50%, 20% of children had unnecessary lumbar punctures. Time from illness onset to treatment was longer in fatal disease (median 18.3, range 8-24 hours), compared with survivors (median 12, range 2-48 hours; p < 0.01, Mann-Whitney U test).

CONCLUSION

Suboptimal treatment in meningococcal disease is due to failure of parents, GPs, and hospital doctors to recognise specific features of the illness. Improvement by public education and better training of clinicians in recognition, resuscitation, and stabilisation of seriously ill children.

Review and consideration of coagulopathies

Blood components bring nutrients to the tissues, remove wastes, provide defenses against microorganisms and foreign bodies, and retain sufficient fluidity to keep the system functioning properly. Coagulation factors are also present in the blood as part of a sensitive system that stems the flow of blood from a wound and maintains homeostasis. These factors include anuclear platelets that originate from megakaryocytes in the bone marrow, as well as soluble factors in precursor form, and calcium ion. Faults in single or multiple parts of this system, which can be determined in the patient's history, may result in bleeding problems that may be clinically relevant. Clarification of coagulation defects requires cooperation with a hematologist before medication that affects the coagulation system is prescribed or before any procedures that may result in bleeding are undertaken.

Blood pressure and diurnal variation in sodium, potassium, and water excretion

The objective of this study was to examine associations of blood pressure (BP) with ratios of overnight to 24-h urinary excretion of sodium, potassium, and water. Each of 125 men 27-64 years of age, not taking diuretics, had BP measured during the day on a Monday. Beginning Monday evening, each participant provided three carefully timed 24-h urine collections, divided into daytime and overnight (bedtime to awakening) specimens. Proportion of total 24-h excretion of sodium, potassium, and water in the overnight specimen, standardised for creatinine excretion, was determined for each 24-h period. Associations of systolic and diastolic BP (SBP/DBP) with these proportions were examined with control for age, body mass index, alcohol intake, and heart rate. Mean BP was 116/71 mm Hg; 15 men were on non-diuretic anti-hypertensive therapy. Mean 24-h urinary excretion was 168 mmol for sodium, 68 mmol for potassium, and 16 mmol for creatinine. Mean overnight to 24-h proportions averaged over the 3 days were 30.7% for sodium, 22.0% for potassium, 32.1% for urinary volume, and 33.2% for creatinine. Partial correlations of SBP and DBP with the 3-day averages were 0.257 (P < 0.01) and 0.210 (P < 0.05) for sodium; 0.223 (P < 0.05) and 0.222 (P < 0.05) for potassium; 0.127 and 0.091 for urinary volume; and -0.033 and 0.014 for creatinine. Correlations for sodium proportions were larger for the first 24-h period, compared to the second or third 24-h period. These results indicate that higher BP was associated with a relatively greater proportion of sodium and potassium excretion at night. Further work is needed to clarify temporal sequence, ie, whether a relatively greater sodium and potassium excretion at night is a risk factor for higher BP (eg, via renal mechanisms), or whether higher BP results in relatively greater sodium and potassium excretion at night, or both.

The roles of activin and follistatin signaling in chick gastrulation

Activin, a TGF-beta family member, and follistatin, an activin antagonist, encode signaling proteins which have been implicated in fundamental events in early vertebrate embryogenesis, such as mesoderm and neural tissue induction, and axial patterning. In this study I examine the roles of activin and follistatin in gastrulation in the chick. Activin betaB is found to be expressed at the base of the primitive streak prior to its formation, consistent with a role in streak induction. Follistatin has a more complex and dynamic expression in Hensen's node, and exhibits a left-right (LR) asymmetry. Antagonizing endogenous activin by ectopic application of follistatin protein causes the partial dissolution of the primitive streak and node, both morphologically and as assayed by loss of expression of molecular markers. This suggests that activin is necessary for the maintenance of streak morphology, and that follistatin may be involved in termination of the anterior progress of streak growth or in suppression of supernumerary streaks. Cell ingression through the node following follistatin application is normal, suggesting that it does not depend on the pit-like morphology of the wild-type node. Finally, follistatin temporally extends the asymmetric pattern of expression of HNF3-beta, this, as well as the stronger right-sided expression of follistatin, suggests a possible role in LR patterning.